Radiotransmitter



June 2 1928. 1,674,740 w W. H. PRIESS RADIOTRANSMITTER Filed Aug. 51, 1922 6 Sheets-Sheet l Q In ventor:

Filit'amEPrf5s a o y l b June 26,

' Filed Aug. 51, 1922 1,674,740 w. H.- PRxEss .RADIOTRANSMITTER Aw I , a Sheets-Sheet 2" Julie 26; 1928.

v w. HLRRIEss RADIOTRANSMITTER 7 Filed Aug1f51. 1922 e Shets-Sheet 4 June 26, 1928.

w. H. PRiEss RADIOT ANSMITTE R -Filed Aug. 31. 1922 6 Sheets-Sheet 6 QNNN b Raw mkN - lnvntor: m'lfiamll Fri ass v 2 to the circuits.

Patented June 26. 192 8 UNITED STATES PATENT OFFICE;

WILLIAM H. PRIESS, OF BELMONT, MKSSACKUSETTS, ASSIGNOR To WIRELESS SPE- CIALTY APPARATUS COMPANY, OEBOSTQN, MASSACHUSETTS, A CORPORATION on NEW YORK.

Application filed August 31;

or variable elements necessary to change the Wave length or foiswitcliing from sending to receiving positions and vice versa may be 10 locally controlled directlyat. the transmitter, yet the invention is more particularly adapted forthe more or less remote control of such elements; that is, for coiitrollingtheir adjustment from adistant point which may 1 5 be a few feet, several miles oreven hundreds of miles from the transmitter.

.At the present time, the circuits of radio transmitters are altered by manually shiftiiig switches or clips connected mechanically It is desirable to. control from some more or less distant pointthe Wave length of the transmitter and in addition to control certain other radio frequency connect-ions such as the. antenna ..or aer al and its connection to ground, and also to control-certain circuits such as the main power circuit and the 500 cycle circuit (if one is present) and the auxiliarycirc'uits, such as the key and generatorfield circuits; At present,

- practically the only circuit controlled at a distance is the key circuit, and this control consists simply in lengthening the relay key. line, determined bythe separation] of transmitter: and operating location.

The advantages of a distant control for the operatingcircuits and for changing the Wavelengths are numerous. For exan' iple,

distances, the instrumentalities at the trans 'mitter maybe actuated to make the adjusta chain of transmittingstat-ions located in desirable geographical positions can be operated from one centralpointj lVhen such ,operation is attempted at the present time,

- instructions must be given the attendants at the transmitter location when changes in I Wave length are desired'.' Such-instructions .45 are given by telephone. This offers distincthindranceto thespeed of transmission and requires an increased maintenance force at the transmitter stations. An important advantage is secured, even when the transn'llt-tGI'"lS only separated a short-distance from the operator, when a full control-of the Wave lengths and operating circuits is made possible at the operating 5 location, I;

, sincehthc' various circuits canbc easily and RAD-IOTRANSMITTEE.

1 92 2 seriaino. 585,464.

rapidly shifted tvithout the operator leaving his table'. Furthermore, the use of a remotely distant control permitted by this invention decreases the cost of radio communication by permitting a station to handle more business in a given time. Still an-' other advantage of the inventionis that the high teiision'a'ntenna lead at the transmitter is at a point remote from the operator and consequently frees him from the danger of accidental contactwith the lead. J

The apparatus used in the present invention for shifting the wave lengths and for controlling the power circuits and shifting from the-sending to receiving positions'and viceversa comprises an electromagnetically operated instrument-ality or instrumentalities at-the transmitter for directly operating the various adjustable and tuning elements, a controlling device or devices at the more or,' less distant point under the control of linking the instrumentalities at the transmitter with the .operators control device-.1"

provide-separate circuits connecting each instrumentality With the control device. However, in cases Where the transmitter and'o'pcrating location are separated long distances, for example, several miles or even hundreds of miles,-it is preferable, and even necessary, to operate and control the trans- For shorter distances, it is preferable to the operator, and an electric" line or lines ments by having the control device at the ators position, I provide a source of direct current and a source of alternating current.

Near the transmitter end and interposed in tliecircuit between it and the operator are located two polarized relays, one operated only-byth'e direct current in one direction and the other operated only by the direct curreiitin the opposite'direction. These relays operate the key and the send-receivesvvitch; A third non-polarized relay isg then rent may be used to control the key.

' impulses caused by the operator.

nism and a wave changer selector,

coils.

provided near the transmitter, which is sensitive to alternatingcurrent only and is connected in series with a large condenser across or bridging the line. The thirdrelay would have a suitable time constant so as to be insensitive to the pulses which actuate the other relays. selector systems at the operatin and transmitting ends of the line controlled from the operators end via the alternating current relay, the circuits at the transmitter controlling the various \vaveslength settings can be controlled. i Y p This method employed'for long distances may be slightly varied; For instance, the polarized relaysoperated by direct current may control a wave changervrelease mecha- Circuits including each wire and ground may be utilized to operate the start and stop mechanism or the send-receive mechanism, while the bridge line operated by alternating pluge wave-length changing mechanism operated will depend on the number of direct current Each time a pulse is transmitted, a damped time element switch is actuated through a magnetic ratchet. The time switch will ultimately close one wavelength-changing mechanism or another, depending on the number of impulses received by it.

The local wave-length adjusting or changing mechanism, which can be controlled from 'a distance by any suitable control de vice and line (depending, of course, on its length), varies or adjusts such parts of the high frequency circuits as will produce the desired wave length,for instance, as here illustrated, theprimary coil, the coupling coil and the antenna inductances or'load- The adjustments for different wave lengths may be accomplished by motors or by other electromagnetic devices orsolenoids which actuate different switchesfo'r throwing in the required capacity and inductance for each desired wave length.

As hereinillustratecLI provide a separate electromagnetic device or solenoid for each wave length except the longest, the transmitter being tuned to the longest wave length when all the wave changer solenoids are in inactive or inoperative position. A similar solenoid is utilized for controlling the send receive connections and thepower and generator circuits. All of the wave changing solenoids must be in inactive position before any of them can be actuated to secure a desired wave length adjustment. This local mechanism can be controlled for a distance by any suitable selector or operating device over two or more wires as above outlined or in the manner herein illustrated and described as an embodiment of the invention.

By the use of synchronized net/4,740

An objectof the invention is to provide a wave length changing control which is speedy andeflicient.

Another object of the invention is to provide, in connection with a transmitter, means for "controlling it from a: distance.

A few of the features among others) of this invention are as follows:

(1) The provision of aseparate actuating device for each wave-len throw in theaproper value primary inductance, couplingindu'ctance and antenna inductance for. each wave length setting desired; v v

(2) Means for switching from sending to receiving by connectingthe antenna to the transmitterand receiver? alternately, ground ing the receiver when the'apparatus is sending.

Means ensuring the opening of all .astuating devices before a new wave length setting is made.

l) The provision of a' short circuiting clip between the secondary of the trans former and the antenna inductances or coils for preventing undue rise of potenial in the high frequency circuits, which would happen if the antenna coils remained .op enlcircuited, this clip setting the transmitter for the longest wave length when the other wave length changing devices are open orin inoperative position. i

The provision of electromagnetic spring controlled devices for changing wave lengths and for changing from sending to receiving and vice versa.

th setting to (6) Theprovision of circuits which enare removed from-the operators-table.

1 (8) Apparatus in which high potentials I (9) A minimum number of switches for each wave length adjustment, one in the primary circuit and one in the secondary'circuit, the secondary switch blade being directly connectcdto a variable tapping point on the secondary coil. i

(10) The longestwave length isproduced .by opening all the wave changer switches,

thus reducing the number of wave changers necessary. The circuits are also always tuned. If the operator actuates the wave changer while the key is depressed, no harmful effect is produced, because ofthis tuning, preventing an undesired rise of potential. 1

(11). Variometer arrangement of loading coils to permit the use of a fixed short circuit' lead for the longest wave length and to provide for avariometer adjustment for the:

' a contact 1 which is connectedby a conduc-.

longest wave length.

(12) The location of a series antenna con; denser, used on'theshortest wave length,--in

' the, lead between the secondary coil'and the switch for thiswave length adjustment.

' (13) The mounting for the'load coils..

In the accompanying drawings, Ihave illustrated an application of the invention to ter and controls;

a quenched spark transmitter in which:

Figure '1 is a diagram of'the various circuits of the transmitter and control; devices; Fig. 2 is a front elevation of the transmit Fig. 3 is a side view thereof; Figs. 4 and 5 are detail views I switch controls for the generator, circuit-s;

Fig. 6 is a sectional elevation o'fan electromagnetic control device;

. Fig. 7 is an end view thereof,

Fig. 8 is a planview thereof;

.' F ig.- 9 is a plan view of the control boxj and YFig. 10 is a sectional view thereof; -In Fig. 1 is illustrated diagrammatically the transmitter radio frequency circults transmitterillustrated is ofthe quenched spark type and comprises a prlmary circuit P having in series therewitlra spark gap SG, primary transformer coil PC andtrans mitting condensers'C. The primary coil PC is' inductively and adjustably coupled by coupling K to the secondary coil SC grounded at G. Interposed between the secondary coil SC and the antenna or aerial A are the inductances or loading coils L which are of the pancake type and are arranged as morefully described hereinafter. Theload coils L are electrically connected at their outer end to the inner end of thesecondary coil SC bymeans of a short-c'ircuiting connection or clip Y while the opposite .end'of the in? ductances L: is connected to aerial A bya' conductor X. In the embodiment here i1 lustrated, theappa'rat-us can be adjusted for four wave lengths; for instance-,for wave lengths of 300, 600, 800 and 1800 meters.

The transmitter is normally tuned storthe 1800 meter adjustment, when all oftlie electromagnetic control devices for the'shorter inductance and of. the loading coil inductances as 'to tune the-apparatus to the wave length desired. In the diagram (Fig. 1),

the transmitter is set for the'No. II wavelength adjustment.-- 4 v Electromagnetic'device I adjusts the ap-' .the- I electromagnetic devices for varying or shift-I "ing the wave lengths and the circuits trolling the electromagnetic devices, Theparatus for the shortest wave-length through posite' end to ,the secondary coil SC at a polntglving the required value of secondary coil inductance 'for. this wave-length.- In

"to'a conduct0r-5 which is clipped at its op the conductor 2 .is'the series antenna or Qshortening [condenser 6. Associated with the device I arethe, relatively movable contacts 7 and 8, the contact S'being connected by. a conductor 9 to. the primary coil PC at A conductor 10 connects contact 7 to the circuit P at a point .10 located between the condensers C and the coil PC. When the dea point to give the right value ofinductance for this wave length adjustment and thecon ltjact 7 being mounted on the actuating arm of the'electromagnetic device I and adapted 'to engage cQntactS'When't-he arm is actuated.

vice I is actuated (assuming that'a-ll devices I I, II, III are in inoperative position), the. contacts 4 and. l-enga'ge, connecting the coil 3 to the coil SC at a desired point through conductor 5, and the contacts and-S'engage, placing the required amount of primary coil PC inductance in the circuit P. Thus when the electromagnetic device I is actuated, the required amountfof primary coil inductancc, secondary coil inductance and loading coil inductance .arefplacedfin circuit for this wave length, the use of two switches only being required, one controlling controlling the secondary coil and loading.- inductances. The condenser 6iisalso placed in circ uit for tllS shortest wave length adjustment upon actuation of device I. ll lien' device I; is actuated, theipri'mary' circuit P' is completed through contacts 7 and 8, conductor 9, coil PC. gap SG,'cond enser C and conductor '10. The secondary circuitis completed through'coil SC, conductor '5, contacts 4? 1 condenser 6 coilfl3, C0nductor 1 the primary coil inductance 'and the other- X and aerial A.:' In like manner, the ,el'ec-p tromagnetic devices II and'III- may be actuated to-th-row in corresponding values of primary and secondary coupling inductances .and .the required amount of loading-coil inductance. For this purpose, there areprovided the fixed or stationary contacts 1, and .l theconnections 2 and 2F therefrom to the required points on the loading 3' and the movable contacts 1", 1, c -acti'ng with contacts 1 and 1 and connected by conductors 5" and 5" tothe required points on the secondary coil SC. The devices II, III also control relatively movable contacts 7, 8 and 7 8" connected by cohductors t)", 9 to the necessary points on I the primary inductance PC and by conductors 10, 10 to the point 10*.

ever/4o transmitter, to the receiving position contact let which connects the aerial to the receiv ing apparatus (not' 'illustrate'd) and is in paced relationto contact 13. NVhen the arm 11'i's in the position shown (thetransmittin'g position), the receiver is grounded at 15 and is disconnected fromithe aerial, but when the arm 11 and contact 12 are-shifted to engage the receiving contact 14, this ground is disconnected. The magnetic de- Vice IV also'controls-ccrtain other circuits (not illustrated) through the switches 16, 17 18 and 19 (illustrated in detail in' Figs. et and 5). control the main line of the 500-cycle generator. Thecontacts 17 are in series with and control the generator field and relay key.

The contacts 18 control automatic starting and stopping devices (not illustrated). The contacts '19 control a discharging resistance in the generator field circuitJ Acrossv the contacts 17 may be placed an arcing con-' denser. A switch on, the panel permits the trated in Fig. 1, it is transmitting and thecontacts 16', 17 and 18 are closed, power being supplied from the generator to the circuitP across the transformer T in the usual manner. When it is desired'to receive, the device IV is actuated in the reverse direction, the plunger 11 upon arm 11 opening contacts 16, 17 and 18 and closing contacts or switch 19, and the'aerial beingftransferred to the receiver contact 14 and di connectedfrom the transmitter This move-- The details of a practical embodiment of switches ment also disconnects ground 15.

1619 and plunger 20 and their arrangements will be described more fully in connection with a description of Figs. 1 and 5.

In Figs. 2 and 3 is illustrated a practical The contacts 16 are in series with and,

and the spark-gap SG.

embodiment of the transmitter assembly and circuits illustrated in Fig. 1. The transmitter as here illustrated comprises a suitable channel iron supportingframe 20, to the front (Fig 2) of whichare secured three insulatingpanels 21,- 22 and 23. The

panels and frame 20 support the aerial lead,

the wavechanger, series antenna condenser, quenched. gap, primary condenser, transformer, meters, starter switches and motor generator controls. ()n the front -of the lower panel 21 (Fig. 2) is mounted a double pole, double throw, fused main lineswitch 2tconnectcd to either the ship line 25 or to a line 26 to a battery source of power. Below switch 24 is mounted the starter or contactor mechanism 27 for the starting and deaccelerating device detail). To the right of the starter 27 is a double-polo fused switch 28 for controlling the 500-cycle line. To'thc left of the starter 27 is a single pole switch 29 for controlling the circuits of the magnetic control devices. Switch 30 controls the generator field and relay key circuits.

The starter 27 may he'of any desired type," and inasmuch as it does not constitute part of the present invention, it is not more fully illustrated. Such starter, for instance, may consist of a main .contactor, two stepwise contactors and a resistance can. The main Contactor on starting closes the motor circuits through the resistance, and the stepwise contactors successively. close asthe motor comes up to speed, cutting out successively resistance in the resistance can. 'On stopping, the main and auxiliary contactors open and the counter E. M. F. of the motor causes the main contactor to close the circuit, which throws the resistance across the motor arInature, providing a dynamic break for deaccclcrating the motor.

Directly on the back of the-lower panel (Fig, 3) is mounted the transformer '1, which is enclosed in a box 31 and is not described in detail,as it may comprise any well-known type of transformer designed according to therequirements of the trans-. mitter. This transformer connects the low frequencycircuits with the highfrequency spark gap circuit.

I Mounted above the transformer is the (not illustrated in series antenna condenser 6, which may com-. prise any Well-known type of condenser adapted for; series antenna use. The wavechanger devices I, II, III and the sendreceive operating device IV are mounted upon the front of the center panel 22 as illustrated in Fig. 2. Upon panel 22 is mounted the relay key 32, the motor field .rheostat 33, the generator-field rhcostat 34 The wave-changers are mounted between the front middle panel 22 and a rear insu lating panel 36 (Fig. 2) spaced and connectedframe20. p The ,fixed primary coil PC is clamped to thefour bakelite tubes 37 between panels 22 A and 36. The coupling or secondary coil SC is movably mounted-directly behirid'the. primary coil PC (Fig. 3) upon a bakelite tube 39, which is mounted for longitudinal movement axially of the coil PC,-t.o.,move' coil- SC towardsand away from coilPC to vary the coupling, .the tube 39 'being'mechanically. connected to a coupling adjustment handle (Fig. 2) mounted at the front onpanel22. .The means for adjusting the coils PO and SC relative to each other is not illustrated in detail, as such means may be ofany desired character whereby the-separation between] the coils may be varied or adjusted. Mount- 4 from terminatingin clips 43 'connectedtothe coupling coil SC at diiierent points for ed transversely of the tube 39 and secured to move therewith is a terminal hoard ll v (Fig. This terminal board is provided with four terminals 42 having leads 42 therecutting. indifferent inductance an; the several wave-length adjustments in the manner v illustrateddiagrammatically in Fig. 1.. One end of the coupling coil SC is connected to a radiation ammeter, the connection being'43.

The transmitting condensers Care mounted-in a rack in front of'the primary-coil PC I cept that for the longest wave-length. The

' and are ,fastened to. the bottom bakelite rods 37. -These transmitting condensers C may be of any desired type suitable for thispurpose.

The four terminal blades 1, 1, 1", 13, are mounted upon the rearpanel 36 (one 'of which l is shown in Fig. 2 These blades or contacts 1, 1 1 13, which were described in connection with Fig. 1, are arranged transversely in spaced relation across the npperportion of the inner side of the panel 36. The blade 13 (not seen in Fig. 2), is connected by conductor to I the'end of the lowest or first loading coil 3. The blade 1- (not seen in Fig. 2) is connect-jv ed by conductor Z to the-variometer of the first antenna coil 3. The blade 1% (not seen) is connected by conductor 2 to the variometer of the second antenna coil 3. The contact or blade 1 is connected by conductor 2 to the var'iometer of the third antenna coil A series of terminals 44,'-four in number, corresponding to the number of blades 13. 1, 1 1 ,-are-moun ted in a line below such blades upon the inner side of the rear panel. 36. The more remote terminal 44, not

seen in Fig. 3, is connected to a lead 45 from the-series antenna condenser 6. Flexible leads 46 connect the movable contacts 4, 4, 4, with terminals 44 (not shown in Fig. 2)

.4 'and 1 engaging, the secon'dstud'44 (if the system' is connected through the series annected indirectly to the terminal block 41 while theshort-circuiting clip Y is shown connected to terminal 44 shown in Fig. 3.

'Directly below the remote terminal 44 is a terminal 44' having av connection 45 to the other side of the series antenna condenserv 6,

' and havingfaflexible lead 44 to it Come sponding terminal on the-coupling coil terminal block 41. lVhen the shortest wavelength device is in position with the contacts tenna condenser 6 to the coupling coil SC. A short-circuiting' clip (not illustrated) may be provided to cutout the series antenna condenser in cases where very short antennae are employed Flexible leads 47 connect three of the'terminals 44 with the terminals on block "41,'while the fourth terminal 44 (the more-remote looking at Fig. 2.) is conthrongh terminal stud-44 A bracket 1 is mounted on the transmitter fra1ne 20 and is provided with a. binding post A which is cohnected to the aerial A. The flexible lead the lower end to movable contact 12 (Fig.

A is connected on nje end to the postand at whereby the aerial may be alternately connected to contacts 13 and 14.

In Figs. 6, 7 and 8, -I- have illustrated the details ofconstruetion of the electromagnetic' actuating or control devices I, II, III, I IV, for the various wave-length adjustments and send-receive switch. The transmitterof this invention has an independent 'conta'ctor' system for each wavelength adjustment ex 0 several electromagnetic local operating decontrol devicescomprise bakelite rods 4 and 11, illustrated diagrammatically in Fig. 1, and structurally in Fig. 3, which slide through and are supported upon bakelite guide pieces 60and 61 (Fig. .3) supported by the upper'members 37. To the rear ends i of the rods 4-and 11 are secured the clip contacts 12, 4, 424, adapted to engage the contacts l3, 1, 1, 1 when the rodsare moved towards the rear as described .above. The closing of these contacts (except contacts 12 1 5 and 13), throwsinto circuit a predetermined value of-aerial inductance L and a predetermined value of the coupling coil SC.

The opposite ends ofrods 4 and llhave slots 62 in which the electromagnetic devices are. pivoted. Each rod 4 or llris actuated as follows. An arm 63 is pivoted between its ends to a projecting bracket .64

on the electromagnetic device casing 65.

rigidly by a part 69- of insulating material,

whereby the circuits are thoroughly insulated from each other. The parts 67 of the system, the device' is stopped by a stop or wave changer devices form the contacts 7, abutment 87 secured to the slide rod4 (Fig.

7*, 7 described above. and illustrated in 8) and adapted to engage the crosspiece '61.

Fig. 1. A rearward movement of any wave 'A quarter-inch hammer action is provided changer arm 63 moves a rod 4 rearwardly between the plunger 74 and arm 63. This is to close the contacts connecting the coil. SC secured by providing a hole 88 in the end 75 and 'inductance's L. The primary circuit P of plunger 74. The arm 63 is connected to (Fig. 1) is simultaneously varied in the folthe plunger 74by means of a pin 89 riding lowing manner: The metal parts 67 (conloosely in the hole 88. The hole 88 isoil tacts 7, 7*, 7 of the arms 63 areconnected center relatively-to the axis of the plunger, to the high potential stud 70 of the primary being located more below the axis'than above condenser system C by leads 71,. correspondit The co-ordination of bumpers, stops, ing to the leads 10, 10 10 illustrated diapawl and spring assures the'presence of the grammatically in F ig, 1, and are arranged to hammer blow at the beginning of both the engage the contact clips 8,8, 8 which are opening'and closin connected by the leads 9, 9, 9 with'the pri-- overcome the static friction.

mary coil PC (Figs. 1 and 3). The clips 8, The system can also be electromagnetically 8, 8 are mounted on cross piece 60. The or electrically operated for control from a outer end of the primary coil PC is condistant point, alternative with operati'oniof nected to one end of the spark gap by a lead handle 78. Around the plunger 74 is coil the condenser, completing the primary cirdrawn outwardly against the spring force 77 cuit P. A lead 72 also-connects coil PC to and the friction of the system. When the thecondenser C for the longest wave length plunger 74 reaches the stop 85, the pawl 79, adjustment. which rides over an enlarged portion of One of the magnet c controls I, II, III, the-plunger 74. locks the latter, dropping I 72. The opposite end of the spark gap SG enclosed in the'casing 65. If the coil 90 'is connected by a lead 73 to the case side of is excited or energized, the plunger 74 is IV for actuating the switch arms 63 is illusinto recess 80 by reason of the spring 81.

trated in Figs. 6, 7, 8,'the.controls being The plunger 74 is in three parts,rightmounted on the front of middle panel 22 of hand-part- 74 (Fig. 6) of enlarged cross Fig. 2. Each control comprises a plunger section, an intermediate part 74 of reduced 74 having an end 75 pivotally connected to. cross section in which the slot 80 is located,

the lower end of arm 63 and slidably mountand sliding in the piece 86, and an outer ed in the casing 65 and extending through part 74 threaded onto the intermediate part panel 22 to the front. Fixed to the plunger and guided in the piece .86. The inner end 74 between its end 7 5 and casing 65 is an of part 74 forms one shoulder of recess 80 abutment ring or collar 7 6 between which and the pawl 79 rides past 74 .when the and the casing 65 ismounted a spring 77. plunger is moving into and from operative A- handle 78v is secured to the opposite end position. Upon the downward movement of plunger 74 in front of the transmitter. of the pawl 79,2111 insulating button 91 on When the handle 78 is pulled out, as indithe inner end of the lever 82 likewise moves cated in full lines, Fig. 6 spring 77 is com downward, allowing a pair of contacts 92 pressed and the arm 63 is moved to close the to open, the contacts 92 controlling the cirswitch contacts. To look the plunger 74 in cuit of the electromagnetic coil 90. The operative position, a plunger pawl 79 is contacts 92, shown in Figs. 2, 6 and 8 and forced into a recess or slot 80 in the rod 74 diagrammati l y n F gpr wp ir by means of spring '81 as the plunger is of transversely-arranged springs secured at too pulled back. A lever 82 pivoted at 83 to their outer ends and overlappingat theirth a i g 65 is also pivotally connected at inner ends and provided with contacts, these 84 to the outer end of the pawl 79, the spring springs normally being arranged to be out 81 being interposed between lever 82 and of engagement with each other except when the casin '65 surrounding the locking demoved into engagement or contact by the vice 79 hen th l v r 82 is depr ssed by upward movement of the button 91. In each hand, it raises the pawl 79 out of locking 1nstance,'as soon as the pawl 79loclrs the engagement .with the plunger or rod 74, alplunger 74', the circuit through the coil 90 lowing the compressed spring 77 to force the is broken upon the'separation of the conrod 74 inwardly to swing the arin 63 to tacts 92 so thatsuch coils 90 are only enerinoperative or normalposition. The lever glzed 'durlng theperi'od of useful work or 82 and locking mechanism is mounted in uring the m ve nt offhe plunger. Atfront ofthe-panel 22 where it is accessible.

engaged, the plunger 74, is stopped by a, con'tacts93 overlappihg at theirinner ends,

tachedto the casing or sh e1l 65 in front of When the wave-changercontacts are fully the collar 76 1s a pair of similar leaf spring brass washer 85 and a tubular shouldering secured at their outer ends to and insulated piece 86 which is fixed relative to the plungfrom the casing 65 and normally arranged to er 74. In the open switch position of the be out of engagement with each other. Con- 'tacts 93iareshown in Figs 6., 7 and 8 and diagrammatically in Fig. 1. Upon the outward movement of the plunger 74, an insulating button 94, attached to the collar or abutment 76, engages the spring contacts 93, closing a circuit including a magnetic coil 95 surrounding the pawl plunger- 79. It will thus. be seen that whenthe plunger 74 moves I outwardly.to-foperative position shown in full lines in Fig. 6, the contacts 93 control-- ling the coil 95asurrounding .the pawl are closed placing such circuitin a condition to be energized (by means to'be-described) in order to move the pawl 79 out of engagement'fj with the plunger 74, allowingthe' spring 77 to move the plunger or mechanism to inoperative:'position. The movement of the plunger 74 to inoperative pos1-.

work has been completed.

A condenser 96 isplaced'acrosstheicontacts92 to quench any tendency of arcing. The contacts 92 and 93 may be of tungsten. The intermediate part 7 4 of the plunger 74 is of Mon'el metal toprevent-short-circuiting of the useful'flux of'the magnets,-.while-the outer part74 is ofsteel to provide a hard- 102. the coil being builtaround it.

tubing telescopes in the rear through the I casing '65 and at the front extends around] encd ledge for thereturned shock of such strength that the material will not be dam-. aged and to reduce friction to a minimum.

All four pairs of magnet systems 90, 95 are rigidly locked to a steel plate 97 which is firmly fastened to the an'gle'iron' frame- Work 20 of the transmitter, openings being: provided in'the panel 22 to allow the handles 78 andthe' pawl mechanisms 82. to be at the front. The construction provides interchangeability, perfect alinementof' moving parts, and reduces the shock' of the system to a'ncgligible' value. The 'system'runs free 1y if Properly oiled.

Each 'ma'gneticsystem may be disassembled by disconnecting the arm 63 from the rod 411 plunger 74 and bracket 64 and removing-it. Remove handle 78 and collar 7 6. Pull the plunger 74,to the right enough to remove the set screw 98 and unscrew. part 7-4 from part 74 and'remove the parts. To

replacethe .main magnet coil 90, remove the screws99 securing the casing 65 to the plate 97. The detent magnet -may be removed by first removing nut at the front. The detent magnet casing 65*? can then. be withdrawn from the mounting rod 86. The main magnet coil 90 is mounted on a brass tubing This movable switch contact m1.

the sto 86. 'DetentmagnetcOiI 95 is likewise built .on a brass tubing 103. Lever arm 82'may be removed by loosening the screws constituting its pivot 83. The casing 65 for the detent magnet 94 has a removable cover 194. The parts may be reassembled in the reverse order.

It has been found by actual experience that rather large forces are required to perform the operating cycle for each electromagn et system. For example, a force of approximately sixteen poundsalong the plunger 74 is necessary to move the system. The magnet for operatrng the' plunger 74 has been designed for an initial force of twenty-three pounds. The spring 77 in a constructed embodnnent of the invention was designed withan initial force of five pounds.

In its closed or compressed position, .the spring 77 has a force in the neighborhood of twenty-fivepounds. Thesystem is quite rapid inasmuch as therejis no residual mag net-ism to hold-the p'lu'ngers 7479 in'the solenoids when a change is desired, since the operation cuts off the current from the solenoid to be operated. The magnet coil control contacts 9293 are requiredto make and break circuits carrying currents in the neighborhood of three amperes, and successfully do this especially when a, condenser is connec'ted across .the contacts.

tance to make the various adjustmentsis illustrated -diagrammatically. in Fig. 1, the operators distant wave length control being l The means or circuitsifor operating the several electromagnetic devlces from a disloo showndiagrammatically at 00., The line LL represents a source ofdirect; current. One. side Zjof the line LL is' connected to a The other side of the line LL is connec'ted'to a terminal of each magnet 90.95 respectively ofthe devices I, II, III, IV. If the'common movable switch or contact arm at is moved intoenj gagement with-the ternnnal 0,, it closes the circuit through any detent"mag'ne t coil 95 in which its contacts 93 are closed, as device II, Fig. 1. This releases the plunger'74 by r-ais-' ing the detent 79.- After this is done, if the contact arm m isswung to engage any desired contact, a, d or e, a circuit is closed through the desired plunger-actuating mag 'Tnet 90, the contact 0 being electrically con'. I

nected to' the coil 90 of system Lthe contact d'being electrically connected to the coil 90 of system II and the contact .0 being electrically connected'to the coil 90 of system III. The circuits 0, d'; -e, including line LL have each interposed in' them the contacts 92 above described. i

System IV for the sendereceive devicej is controlled by the send-receive switch S'R; i

The movable member of theswitch Sims electrically connected to theside L ofl" LL, the other side of the line LL being can;

nected to 21v terminal of the coil 90 and to a terminal of coil 95 respectively of device IV. When the send-receiveswitch SR is-movetl to a position in engagement with the con-- tact 1, it closes a circuit through the coil 95 and closes contacts 98 for the purpose of raising its detent andthrowing the plunger 11 from the transmitting position on control 13 shown to receiving position on control 14. lVh'en the switch SR is moved into engage ment with the contact 0, system IV being in receiving positiolnthe coil 90of that system will be energized to drawback its plunger 74 and changing to the transmitting position, ontact. 92 being now closed.

l-laving dertcribcd a general scheme of con trolling the several electromagnetic devices from a distance as illustrated in Fig. 1, a control panel 0C, Figs.9 and 10 will now be described. This distant control device ()0 consists of a metal panel 105 adapted for desk mounting upon; which is mounted a small transmitting key 106 for operating the relay key on the transmitter and;a large T transmitting key 107 for operating the transmitter directly. On the panel are mounted the send-receive. buttons 108 (Fig. 9) controlling the switch 109 (Fig. 10)

' for controlling send-receive device IV at'the transmitter. l

The mechanism 110 on control panel 105 of Figs. 9-10 will now be described. At the rear of the panel (Fig. 10) is secured a vertically-arranged insu ating board 111 having ten external terminals 112. mounted thereon. Eight of these terminals are-in low current control circuits connectedto-the distant transmitter for controlling the wavechanger devices, relay key and send-receive device of Figs. 13.' Two of these terminals are for heavy leads in circuit with the key 107 and connected to corresponding, terminals on the transmitter of Figs. 1-2. Two tel mi nals 113 in addition to the above ten connect to theudetector binding posts, and are for the purpose of short-circuiting the de-'*.

ed below the adapted.

tector during transmission. This short-circuiting is accomplished by the send-receive] switch 108', 109. Across. the small key 106 is placed a condenser. The live parts mountpanel 105 are enclosed in a;

placed in any of the openings 115. The handle 117 is swivelled by means of a bolt 118 to oneend of a channel-shaped arm 119 universally pivoted to allow the handle 117 to be raised out of each hole 115 and to be swung to and into any other hole, the bolt 118 terminating at its lower end in an'insulating button 120 adapted to engageand close the contacts 116 (corresponding to contacts 0, (Z, c, Fig. 1).

To allow the universal movement of the lever or arm-119, the panel 105, at a point constituting the center of the arc on which the'holes 115 are arranged, is provided with a bearing opening 121. Rotatably mounted in this opening is a tubular-member 122 hav- ,ing a pair of ears 123 at its upper end, The

arm 119 straddles these ears and is pivoted theretoby means of a-pin 124.

Slidably mounted through member 122 is a pin or plunger 125. plunger 125-is a spring 126 within themember 122and held in place by a cap 127. The spring 126 teiids tomaintain the plungcrin elevated position, engaging an'abutment 128 secured thereto. The lower end of plunger 125 below cap'127 has an insulating head 129 which when depressed engages and closes a pair of spring contacts 130 (corresponding to contacts A, M, Fig. 1).

YA spring washer 131 is interposed between- Surrounding the the cap 127 and the bearing of the panel to provide frictional resistance to the rotation of the 'member 122. The plunger 125 is depressed when the handle 117 is lifted out of a hole 115. For this purpose, a bar 132 is pivoted at a point 133 between its ends to the ears 123, extending at oneend between 3 the upper end of. plunger 1 25 and, pin 124 and extending at its oppositeend over a Cross pin 134 secured to arm 119.

The upper one of each set of contacts 116 i is electrically connected to binding posts 135 which are electrically connected together'by a strip 136 and have a common external binding post 112*. The lower of contacts 116 are separately mounted on panel 111-and electrically connected to external binding posts 112 The contacts 130 are mounted on an insulating'panel 137, the upper one being electrically connected to a binding on panel 137 and post 138 being connected by-a conducter 139 to one of the posts 135.

post 138 The lower c'ontact'130 is electrically connected to a conducting rod 140 mounted in panels 111137 and forming an external binding post 112. The upper contacts 116,

'130, one terminal of'the send-receive switch 108 and one terminal of key 106 are connected to binding post 112*. The other terminals of the send-receive switch .108 are connected to the'external binding posts 112 and the other terminal of the small key 106 is connected to binding post 112 The large key 107, is connected to external binding posts 1'12 (Fig. 9 The binding-posts 112 are connected to the detectorfor short circuiting the detector from the switch 109, External wiring-is provided to the necessary elements on the transmitter and .to the source of direct current for operating-the send receive switch IV, Wave cha'ngersI, II,-III

and relay key 32. When the handle 117 is raised to disengage'a pair ofcontacts 116 below an opening 115, the movementof arm 11.9 around its pivot 124 will raise the end of bar 132' above pin 134, the: rear endof the bar depressing the plunger 125, closing the contacts 130. .When contacts. 130 are :closed, any electromagnetic device I, II, III

sired wave-length adjustment. "When the handle 117 is placed in another 'open1ng115, .an'other wave-length adjustment is secured and the contacts 130 are operied; r

The actuationof "the operators wave.-

length control 117 ensures that allthe -elec'-.

tromagnetic devices I,II, III of the trans mitter must-be'first opened-before a new.

wave-length adjustment can'be thrown I'in. These several adjustments may be secured by a single movement of the control handle .length adjustmentrequiring no operation of electromagnetic control devices. The wave' length; opening-115 marked 1800, therefore to difl'erent positions, thelongest wave.-

- requires no switch contacts therein, 'andis merely a dead .hole to indicate the longest.

wave-len'gth position.

In Figs. 4 and '5 isillustrated a structural embodiment ofthe switches for the local circuits controlled by'the send-receive con- 'trol IV and illustrated diagrammatically in Fig. 1. The several switches 16, 17,-1.8

and 19 are S8C11I'6(l 't0 an insulating base 145, in turn securedto the rearof the middle panel22 (Fig. 3) at a point in line with rod 11 ofdevice IV. Eachxswitch is mounted .on angle brackets 146 secured to base 145 and having terminals 147 for connection .to the circuits controlled by the switches. The switch 19 comprises a pair of metal arms 148 secured flexibly to brackets 146 by means of'leaf springs '149 secured to their sides and to the brackets. Leaf springs 150 are likewise secured to the brackets 146 and engage the opposite sides'of arms l48 to maintain spring pressure on them when displaced or separated. Thev arms 1-48 diverge .at-their. outerends 151.

Secured'to one arm 148 is a metal loop. 152 which extends around the other arm and is provided with a contact 153 normally out of engagement with the arm but adapted to contact therewith 'when .the' arms are separated. The switches 16, 17 and 18. comp ri se also metal arms 154 which are fieiriblyconneicted to their brackets byleaf springs 149 and have contacts 155 se'-.

by the switches. The arms 154 likewise diverge at their outer ends 156,- butare an insulating switches are actuated -b to the forward wedge plunger 11 secure cured to their inner sides. -Leaf springs 150 bear againstthe opposite Lsides of the arms 154 to maintainthe contacts 155 in engagement to close the circuitscontrolled shorter than the arms 148. The' several 1 end of rod 11.. The plunger 11 has a metal pin I151 adapted toenter between the arms- 148, closing the" circuit across them. The-plunger 11? after the circuit of switch .19 is closed, enters between the arms 154 opening" the circuits controlled by them.

Upon the withdrawal of thelplunger 11 circuits 16, 1'7 and ,18 are closed and circuit 19. opened. The transmitter-is then in the' transmitting position.- The circuits controlled switches 16, 17, 18, 19 were mentioned above. The switches 16 5-19 ar'e'illustrated in Fig. 3,,the' plu nger 11 being slidably supported .in crosspieces '6061. (The. transmitter is in receiving positionwiththe plunger 11? engaging the contacts.) The contact blade -12, whichis connected to the antenna through'lead'A is disconnected from blade 13 on panel 36 and.

is connected to blade 14 mounted on piece 61 and connectingthe aerial to the receiver;

These parts are not seen in Fig. 3, but their arrangement isshownin Fig. '1.

Direptly-behind the top panel 23 (Fig.

-is. locatedthe antenna load coil. system L, the systemconsistingof seven concentric pancake coils 3, 3*, .3", etc., whose axis is perpendicular'toithe axis of the primary and secondaryroils PC,- SC. The'f our lowest coils have variometer attachments with coil system in circuit on the shortestwave length. v Continuous tuning control of the shortest .wave length is provided by the lowest v'ariometer handle 15 7 onfthe front variable portion of coil'3 Tuning co nmanual. controls 157-pro'jecti1ig through the front of the; top panel. The lowest variom eter is the only portion of 'the antenna. load 0f the panel. The-nextlon'gest wave length has in circuit a portion of either the whole or half of the lowest variometer coiland the 7 trol forthis wave length is provided byathe I second 'variometer handle j157. The next longest wave length has in circuit portions of the twolowest varionleter coils and the variableportion of coil 3. The wave length is tuned by the third. variom'eter handle 157 from the bottom. The longest .wave length has in series 'portionsof the-three lowest coils, a variable portion of the fourth lowest coil, and portions of the three-top coils. This wave length is controlled --by the top variometer'handle 157. The coils areseparated by fixedinsulating tubular spacers 158 which provide alinenient for the variometer shaft handles and determine the voltage safety factor between successive coils. When the set has been tuned for the several wave-length adjustments, the va riometers 157 may be independently locked by means of the locking devices 159 to the right 'of' the varioiiicter shafts on the'front of the panel 23.

' switch 164:.

The mounting for the coils 3, 3 3", etc.,

comprises lowcr insulating blocks 160 mounted on tubes 37 and in wliichiare secured verti cal insulating shafts 161. Threaded on shafts 161 are the insulating spider frames obtained with eleven units in the circuit.

The rack contains spring members 166 which provide sufficient clamping for holding the units in the rack on their guides and which will close the gap circuit, should one of the units be removed. The entiregap is placed across the transformer T (Fig. '1). This prevents the posibility of potential exceeding the value limited by twelve'series gaps. The gap switch 164 is arranged so that it successivelycuts in more units 165 as the switch is moved to the right facing the panel. It-

functions to short-circuit gaps to its right.

Upon the upper panel 23 (Fig. 2) are mounted the meters 167, the variometer controls 15? and four push button switches 168. There are three meters. One is a'double scale voltmeter for reading the D. C. voltage or the gei'ierator voltage. One ofthe push button switches 168 mounted below the volt-- meter permits the choice of A. C. or D. C. reading. The radiation ammeter is of the y usual thermo elementv type and accurate over the range of 300 to 2000 meters. The wattmeter is calibrated for 500 cycles. All meters possess a high damping and have calibration accuracy of plus or minus two per cent with the currents, voltages and powers on which they function in the transmitter.

One of the push button switches 168 gives the operator the choice of either stopping the motor generator each time the send-receive switch is thrown or permits him to keep the'motor generator running when the antenna switch is in the receiving position. Another switch 168 controls the key circuit and gives the operator the choice of operating the transmitter by .either the hand key or the relay key,

which are located on thecontrol unit. The other push button switch 168 functions,, to

imam-o cut in an additional fixed resistance in series with the generator rheostat so as to permit a further decrease of generator voltage over the voltage range permitted by the rheostat alone. This resistance is of such value that an overlap is obtainable in going from the highest resistance in therheostat to the fixed resistance and the lowest resistance in the rheostat, ineffect, providing for acon'tinuous variation in voltage from, the voltage for full power to the voltage necessary for 60-watt operation.

The transmitter herein illustrated, to which the control system of the present invention is applied, is of the musical quenched spark, athousai'id sparks per second type. The transfnitterhas a wavelength range of 300 to 2000 meterson antennae of capacity .0008 mfds. to .0016 mfds. The transmitter may be adjusted to any four-wavelengths in this range.

The power rating of the transmitter is based upon the input into the primary radio frequency circui The present invention, however, is applis cable to other types of transmitters. Where tube transmitting systems are employed, very much lighter mechanical systems can be em--" ployed for'changing' the wave lengths. For

example, in a tube transmitter system in which the wave length is obtained by a master oscillator tube oscillating at radio frequencies and with the radio frequency impulses impressed on an untuned amplifier bank of power tubes, the wavev length may be changed by a lightcontact system regulating the 0s cillator tube. i

For are transmitters, various solenoid or motor-driven devices controlled from a distance as above described may be employed to strike the arc and to vary its length and to control contacts, etc, controlling devices such as the cooling pump and the carbon ro-. tating motor. Distance controls of the char- 'acter above described may also be used tocontrol the radio frequency and power-" eir cuits of a high frequency alternator.

I .have thus described a highly efficient type of control'systcm changer which may.

be operated at a distance to control the various adjustments, these adjustments being secured individually for each adjustment :by-

means of electromagnetic controls, although motors or othersuitable instrumentalities may be employed. lheinag-nets. however,

are energized only during the time of useful work, and are automatically cut off at the end.

of that time. These devices are'coiitrolled electromagnetieally in one direction, and by a spring in the opposite direction. I

Each wave-length adjustment is secured by closing one contact in the primary circuit and one contact in the antenna circuit,

thereby reducin the numberof contacts to a minimum. T e longest wave-length adjustment in this system is secured by a shortcircuiting clip Y (Fig.

' 1) connecting the antenna coil' system L and the secondary coil SC directlyfa'nd closing theprimar'y coil PC directly through the common lead of the primary coil system. Thejs'ystem is tuned to the longest Wave length when all of the wavcchanger switches are open.

' advantage, aside from the saving of a wavechanger device for the longest wave length isthat both the primary and secondary circuits are thereby. connected in tuned relation on the open position of all the wave-changer switchesl Therefora'if an operator operates his wave-changer while the key is depressed,

'no' harmful effect is producedyinasmuch as theiinterim bctwcen'theopening of one set of contacts the closing'of another set of contacts for the shorter wave lengths-iscoveredby the transmitter functioning ona tuned position, thus effectually preventing-a rise in potential of either the primary or secondary systems above operating poten- In this wave-changer, the antenna lead is. swung directly from the transmitter to the'receiVer thje receiver antenna post being I located on the transmitter and being connected to ground when the :antenna lead is on the transmitting connection". This ground is removed by the entrance ofthe antenna'blade 12 (Fig.1) into the receiver clip 14. By grounding the receiver. during transmitting',' the capacity efiect is mini-v mixed In the first, second and third coils from the bottom, the variometer arms connect directly tothe switch clips 1, 1, 1? of the wave-changers. In the fourth coil from the bottom, the variometer is 'in series with the outer end of.th'e fifth coil from the bottom, and-theouter end of the'fourth coil from thebottom isin'series with the inner end of the third coil from the bottom'.' This connection permits the use ofa fixed shortcircuit lead Y for the longcstwave-length,

and also provides a variometeradjustment in' this wave lcngth.'-

I claim I.'

11. The combination with .a radio 'transmitterincluding ajcircuit tobe controlled, of a panel on the back of which "are. supported parts of said-transmitter; .a switch for said circuit mounted on the rear of said panel;

a phingencasing mounted on the panel; a

" plunger extending thru the panel und con- -nectcd to operate saidtransmitter circuit switch; a locking meinbenholding said" switch-operating membenin the'position to which it has been moved by its magnet to operate said transmitter circuit switch; a

master-switch -f.or said elcctromagnet and vlocated more I or-less remote therefrom; a

second switch inthe circuit of the electroinagnet of said switch operating. member; means'carried by said switch operating memher and opening said second switch after the lockingmember reaches its position holding 1 said switch-operating member; means resloring said switch operating member, said scc- 0nd switch, and said transmittercircuit switch to their. initial-positions; wherein the master switch is'operativeon the electromagnet of said switchoperating member;

and means moving said flocking member fromts said lOCklIlg'POSlUOII and perm1tting operation of said restoringmeans.

. 3.. The-combination with a' radio trans-. mi'tter'including a circuit to be controlled, of a switch "for said circuit; a member con-- nected tooperateisai'd transmitter circuit switch means operating said- I switch operating member to operatesaid switch; alocking member holding said switch in theposition to which it-has been-moved to operate said trans- ,mittr' circuit switch; meansrestoring said switch operating member and switch to their'initial-positions; an electromagnet removing said locking member from its locl ing position and permitting'thcj operation of said restoring means; a master switch for .said 'electromagnet and located m ore or less remote therefrom; a second switch for the circuit of said electromagnet; and means operated by movement of aid' transmitter switch operating'member 'towardits locked position; and closin said second switch,- thereby putting saig electromagnet circuit and locking memberin condition to be *operatcd-by said master switch and permit operation. OfSRlCl restoring means. A. The combination with a radio transvtoo mitter including a circuit to be controlled; of

aswitch torsaid circuit; an, 'electiomagnetically operated member connected to operate said switch; a'locking member holding said switch 1n 831d operated' position; means mov ngsald locking member into such looking, position; means restoring said switch operating member "and transmitter circuit switch to their initial positions; an electro--' magnet moving said locking member from its lockingposition, permitting operation of- I said restoring means; master switching means controll ngboth said eleclromagnets,

and-located more or less remote thereirom;

a second switch in the circuit of the electromagnet of said transmitter circuitswitch operating-member and means carried by said locking member and opening said second switch after the locking member reaches its locking position; and a second switch in thecircuit of theelectron'iagnet of said lockng member and means carried by the switch operating member and closing said. second switch after the locking member is in locking position; all whereby the operation of the transmitter circuit switch is controlled by said master switching means, and said electromagnets are energized ,only while moving the switch operating member and locking memberrespectively. I

' '5. The combination with aradio trans mitter including a circuit to be controlled, of a switch for said circuit; an operating memher for said switch; a lock for said switch; an operating means for said lock; manually operating means operating said switch operating member and lock operating means; electromagnetic means operating said switch operating member and lock operating membei alteiaiatively with said manually operatively means at will; and master switching means more or less remote from said electromagnetic means and operatingmembers, and controlling said electromagnetic means, all whereby the operating movements and looking of said transmitter circuit switch are controlled by said master switching means.

6. The combination with ,a radio transmitter including a circuit to be controlled, of a switch for such circuit; a spring; an electromagnct operating said switch and also said spring to place the latter in condition to restore the former to its initial position; a lock holding said switch in the position in which it is moved by said electromagnet; an electromagnet disengaging said lock and permitting restoration of said switch by said spring; and master switching".

means controlling both said electromagnets and located more or less remote therefrom. 7. The combination with a radio transmitter including a circuit to be controlled,

of a switch for said circuit; an operating member for said switch; a lock for saidv operating member; and means for operating said operating member-and said lock.

8. The combination with a radio transmitter including a plurality of circuits changing the wave length thereof, of a plurality. of Wave changing switches con trolling said circuits; a plurality of electro-'- magnetic devices operating said switches; and master switching means controlling said electromagnetic devices and located more or' less remote therefrom; each electromagnetic switch and the master switching means being co operatively constructed to cause restoration. of each switch fromitsoperated position by the master switching means prior to the operation of any other of said electromagnetic switches by the master switching means. v

9. The combination with a radio transmitter tuned normally to a given wave length and including a plurality of circuits. chang ing to different wave lengths from said normal wave length; of'a plurality of wave changin switches" controlling said circuits; a plurality of electromagnetic dBVlCQS'OPGI' ating said switches; and master switching means controlling said: electromagnetic devices and located more or less remote therefrom; each electromagnetic switch and the master switching means being co-operatively constructed to permit restoration of each switch from its operated position prior to the operation of any otherof said eleotromagnetio switches; and the transmitter preserving its said normal wave length between operations of said successive switches and at all times when none of said switches is in its operated position, thereby preventing undesirable rise I of potential during intervals between wavelength adjustments.

10. The combination'witha radio transmitter including a plurality of circuits changing the wave length thereof, "of a plurality of wave changing switches controlling said circuits; a plurality of electromagnetic devices operating said switches; and master switching means controlling said electromagnetic devices and located more or switches each controlling said secondary and loading coils; a plurality of electromagnetic devices operating said switches; a connection between said secondary inductance coil and i sa d loading C01lS Wl11Cl1 connection is normally maintained; and a master switching means controlling said electromagnetic devices and located more or less remote therefrom. i y

12. The combination with a radio transmitter and receiver, of a send-receive switch, said transmitter including a plurality of wave changing circuits; a plurality of switches controlling said'wave chapging circuits; a plurality of electroma netic devices operating said send-receive. switch and said wave changing switches; and master switching means respectively controlling the elec tromagnetic devices operating said send-receive switch and the-electromagnetic devices operating said wave changing switches said master switching means both being" located in the same vicinity and more or less'remote from said electromagnetic devices.

'13. The combination with a radio transmitterand receiver and a common aerial for said transmitter and receiver, of a sendreceive switch by which the receiver? is grounded while the transmitter is opera' tively connected to-said aerial; anelectromagnetic device operating said switch; means for lockingthe switch in its position connecting the transmittento the aerial a master switch controlling said electromagnetic device and located more or less remote therefrom; means controlled ,by'said looking device for'open-circuiting said electromagnetic device; and means independent of the electromagnet of said devicefor'restor ing. said switch to its initial position when I released from said locking device.

- '14. The combination with a radio transmitter includin'g'a secondary coil, and 'a plu- -rality of circuits changing its wave length,

of a pluralit of wave-changing switches controlling said'cir'cuits; a plurality of elec}v tromagnetic devices operating said switches; and an antenna-shortening condenser connected between the transmitter secondary coil and the switch efiecting change to the from controlling said coils; .a plurality. of electro- .magnetic devices operating said switches; a

connection between said secondarycoil and said loading coils which is normally maintained; an antenna-shortening condenser connected between the transmitter secondary coil. and the switch efifectin'g the change to devices and located therefrom.

the shortest wave length; and-master switching means controlling said electromagnetic moreor lessremotely 16.'The combination with a radio trans-' mitter including a circuit to be controlled," ot aswitch controlling said circuit, an electromagnetic' device operating said switch;

I v a lock holding said switch in its operated po- -swit'ch controlling said vswitches for saidgoperating circuits; said sition; an electromagnetic device disengaging said lock from said switch'; means opperated by-the lock to-open-ciircuit the electromagnet of said switch, means operated byythe switch to close the circuit of the electromagnet of the lock, and-a master switch constructed to open-circuit] the electromagnet of the switch in .one movement of the 'master switch, and to close the circuit of the electromagnet of the lock' in another movement of them-aster switch.

17. The combination witha radio transmitter. having a permanent normal wave lengthfof a plurality oflcircuits changing-- such wave length to other values; a plu-ral-v itly ofswitches controlling said circuits a p uralityof electromagnetic devices operating said switches; and a master switch con,- trolling said: electromagnetic devices, said master switch and said electromagnetic,

switchesbein-g co-operatively constructed to I open'on'e switch before closing"a nother, and

3 the transmitter resumin its permanent nor malcwave length in theinterval between the opening of one of said switches and the clos ing of another.

118. The combination with'a radio'transvmitter including a plurality. of circuits changing the wave length thereof and a plurality of other transmitter operating circuits,

of a plurality of'switches controlling said,

wave changing and. operating circuits; a. plurality of electromagnetic devices operating said switches; a master switch controlling a plurality of said electromagnetic wave changing switches; and a second ,ma'ster master switchesbeing located in the same v cinity andmore or less remote from said evices. I

electromagnetic g PRIESS;

electromagnetic 

